Rose Loomis and her older, gloomier husband, George, are vacationing at a cabin in Niagara Falls, N.Y. The couple befriend Polly and Ray Cutler, who are honeymooning in the area. Polly begins to suspect that something is amiss between Rose and George, and her suspicions grow when she sees Rose in the arms of another man. While Ray initially thinks Polly is overreacting, things between George and Rose soon take a shockingly dark turn.